IOWA CITY, Iowa (AP) – The University of Iowa Burn Treatment Center is reporting a higher-than-normal number of patients suffering from anhydrous ammonia burns. The center says it has treated five people in the last two weeks. The center’s medical personnel say they usually only see one or two cases each year. Official say the high number of patients in such a short amount of time is concerning.

Anhydrous ammonia is used legally by farmers as a crop fertilizer, but is often used, too, for the illegal manufacturing of methamphetamine. The colorless, pungent gas can burn the eyes, throat, skin and damage lung tissue at high exposures.